Gas pump of a liquid-ring type

ABSTRACT

A gas pump of a liquid-ring type whose housing structure has a first suction opening and a pressure opening at the respective localities where the liquid ring, formed by centrifugal force during operation of the pump rotor, penetrates most deeply and least deeply into the intervane spaces of the rotor and is additionally provided with at least one further suction opening which is located between the first suction opening and the pressure opening. The additional suction opening, relative to the direction of rotor rotation, has its leading end spaced from the lagging end of the first suction opening an amount equal to, or larger than, the vane division of the rotor. A suction duct is connected to the additional suction opening which is separate from the suction duct that communicates through the first suction opening with the interior of the pump housing.

United States Patent [72] Inventors Kurt Mugele, Erlangen; PaulSchnapper,

deceased, late of Erlangen; by Lotte Schnapper, sole heir, Erlangen,Germany [21] Appl. No. 798,274 [22] Filed Feb. 7, 1969 [45] PatentedApr. 20, 19711 [73] Assignee Siemens Aktiengesellschaft Berlin, Germanysaid Mugele assignor [32] Priority Mar. 15, 1968 {3 3 Germany [31] P 1678 604.2

[54] GAS PUMP OF A LIQUID-RING TYPE 8 Claims, 1 Drawing Fig.

[52] U.S. Cl 1. 417/69 [51] Int. Cl F041 19/00 [50] Field of Search230/45, 46, 79; 103/2, 5; 417/68, 69

[56] References Cited UNITED STATES PATENTS 3,006,533 10/1961 Adams230/79 3,228,587 1/1966 Segebrecht 230/79X 3,239,131 3/1966 Whyte 230/453,315,879 4/1967 Jennings 230/45 3,481,529 12/1969 Mugele 230/45 FOREIGNPATENTS 1,139,232 11/1962 Germany 230/79 Primary Examiner-Carlton R.Croyle Assistant Examiner-R. E. Gluck Attorneys-Curt M. Avery, Arthur E.Wilfond, Herbert L.

Lerner and Daniel .1 Tick ABSTRACT: A gas pump of a liquid-ring typewhose housing structure has a first suction opening and a pressureopening at the respective localities where the liquid ring, formed bycentrifugal force during operation of the pump rotor, penetrates mostdeeply and least deeply into the intervane spaces of the rotor and isadditionally provided with at least one further suction opening which islocated between the first suction opening and the pressure opening. Theadditional suction opening, relative to the direction of rotor rotation,has its leading end spaced from the lagging end of the first suctionopening an amount equal to, or larger than, the vane division of therotor. A suction duct is connected to the additional suction openingwhich is separate from the suction duct that communicates through thefirst suction opening with the interior of the pump housing.

GAS PUMP OF A LIQUID-RING TYPE The invention relates to a gas pump of aliquid-ring type and preferably to pumps for evacuation purposes.

Pumps of this type comprise, for example, an approximately cylindricalhousing partially filled with liquid such as water, in which a vanerotor is eccentrically journaled, the housing being covered on bothaxial sides of the rotor by control plates of which each is providedwith suction and pressure openings for the medium to be pumped, thesetwo openings in each control plate being arcuately spaced from eachother. The rotation of the rotor causes the liquid, hereinafter referredto as water although other liquids are also applicable, to be flungoutwardly and thus form along the inner periphery of the housing a waterring which rotates with the rotor and which is guided on a raceway spaceformed by the housing conjointly with the appertaining two control discsof the housing structure. The rotating ring of water conjointly with thevanes of the rotor forms respective cells which during rotation of therotor periodically enlarge and thereafter reduce in volume.

The housing structure, or more specifically the abovementioned controldiscs, have suction openings in the form of arcuately elongated slots atthose localities where the cells commence to enlarge their volume, thatis, where the ring of water reduces its depth of penetration into theintervane spaces of the rotor. The gas to be delivered or evacuated isinducted into the cells through these suction openings. During thecontinued rotation of the eccentrically journaled rotor, the water againpenetrates more deeply into the intervane spaces thus reducing the cellvolume with the result of compressing the gas enclosed in each cell. Thepressure openings, also preferably designed as arcuately elongatedslots, are spaced from the suction slots by an angle of approximatelyl80. When each cell during rotary travel reaches its point of highestcompression, it communicates with a pressure opening so that thecompressed gas is ejected.

Gas or vacuum pumps of the type described are generally known andavailable in the trade. Reference may be had, for example, to GermanPat. No. 269,531 (single-acting pump) or to U.S. Pat. No. 1,718,294(double-acting pump).

In practice, vacuum pumps of the type described above are employed forsingle-stage action in pressure-ratio ranges of about 1.5 (for example500 Torr to 760 Torr) to about 25 (for example 30 Torr to 760 Torr).When the pressure ratio is low, the pump discharging pressure (forexample 760 Torr) is attained relatively early; hence the pressure slotshould likewise commence at an earlier point of the rotational rotortravel and consequently, as seen in the peripheral direction, should begiven a longer arcuate extent. Analogously, for a larger pressure ratio,the pressure slot should have a considerably shorter extent. Foreconomic reasons the sickleshaped pressure opening is normallyconstructed for a relatively large pressure ratio and hence is maderelatively small. In order to prevent excessive compression andturbulence losses when operating at a lower pressure ratio, that is, ata higher suction pressure, the housing structure is provided with a fewbores located slightly ahead of the sickleshaped pressure openings,likewise seen in the direction of rotation. Those bores that are locatedin the region of the discharging pressure, readily permit the gas topass through, whereas the water located on the backside of the controldisc covers all other bores located in the region of lower pressure.

The valve action is even more effective if the abovementioned bores areprovided with ball valves whose balls open or close in dependence uponthe pressure ratio.

The described pumping cycle in each case is predicated upon the presenceof a liquid ring which more or less enters into the intervane spaces ofa rotating pump rotor, as well as upon at least one suction opening anda pressure opening arranged at the respective localities where the waterring has substantially the shallowest and deepest penetration into theintervane spaces. All gas pumps of the liquid-ring type are predicatedupon this fundamental principle of design and operation, including allof the known modifications of this type of pump.

It is an object of the invention to improve liquid-ring pumps for gaspumping purposes with the aid of relatively slight structural changesand additions, in such a manner as to improve the efficiency of the pumpand enlarge the available possibilities of use.

Another object, conjoint with the one just mentioned, is to devise a gaspump of the liquid-ring type which is capable of performing the functionof two pumps for respectively different suction pressures.

Another object of the invention is to provide a pump applicable formixing and conveying gases and/or vapors for the purpose of performingchemical reactions within.

It is still another object of the invention to provide a gas pump inwhich the occurrence of cavitation is avoided.

To achieve these objects, and in accordance with a feature of theinvention, a pump generally of the liquid-ring type is provided with atleast one additional suction opening located between the normallyemployed suction opening and the pressure opening. Seen in the runningdirection of the pump rotor, the additional suction opening is spacedfrom the end of the first-mentioned suction opening by an arcuate amountat least equal to the vane division of the rotor, and a separate suctionduct or conduit is provided to communicate through the additionalsuction opening with the interior of the housing structure.

The invention will be further described with reference to an embodimentillustrated by way of example and partly in section on the singleillustration presented on the accompanying drawing.

Shown on the drawing is a gas pump of the liquid-ring type designated byl, the illustration of the pump being schematical and with the circularcontrol disc facing the observer and forming part of the housingstructure removed to expose the interior. The housing structure furthercomprises an approximately cylindrical housing portion 3 which at bothaxial ends is enclosed by the control discs of which only the rear disc16 is visible. A rotor 2 carrying a number of uniformly distributedvanes around its peripheral surface is eccentrically journaled in thehousing and, during operation of the pump, rotates in the clockwisedirection indicated by an arrow 17.

The gas to be delivered is confined in a vessel 10 which is connectedwith the suction duct 8 of the liquid-ring pump 1. The duct 8communicates through a suction opening 5 in the control disc 16 with theinterior of the working space of the pump. The suction opening 5 isarcuately elongated to the shape of a crescent or sickle, or rather, toonly one-half portion of such a shape. Through the suction opening 5,the gaseous medium is inducted into the pump space where it enters intoa cell formed between each two adjacent rotor vanes and the rotating,eccentric ring of liquid. As described above, the gas enclosed in eachcell is compressed during the clockwise rotation of the rotor until itis ejected in compressed condition through the pressure opening 4 of thecontrol disc 16. For vacuum producing purposes the compression of thegas is up to the atmospheric pressure obtaining at the pressure duct orconduit 9 of the pump.

According to the invention, the pump is further provided with anadditional suction opening 6 in the control disc 16 which forms part ofthe housing structure. Another suction duct 7 communicates through theadditional suction opening 6 with the working space of the pump. Thesuction opening 6, relative to the direction of rotor rotation, isspaced from the end of the first suction opening 5 by an arcuatedistance corresponding at least to one vane division I so that the twosuction openings 5 and 6 are always separated from each other by atleast one rotor vane. The additional suction opening 6 extends, relativeto the rotational direction, approximately into the region where thewater ring 19 again enters into the vane interspace of the rotor up tothe region of commencing compression. The rotor cells passing by thesuction opening 6, if no gas were inducted through the suction opening6, would have approximately the same gas pressure as obtains at thesuction duct 8.

The gas quantity Q inductable through the additional suction opening 6can be determined by the following Paw in which Q, denotes the inductedquantity of gas, p the suction (induction) pressure, =prpdenotes thepressure difference between induction pressure and vapor partialpressure in the region of the suction opening 5; and Q p denote thecorresponding physical data in the region of the additional suctionopening 6. The additional gas quantity Q can be inducted through thesuction conduit 7 under the suction (induction) pressure p For operationat high pressure ratios it may be preferable to have the end of theadditional suction opening 6 located in the region of compression.

If required, one or more precompressors, for example an ejector as shownat 11, may be connected to the additional suction duct 7 ahead of theadditional suction opening 6, the precompressing ejectors or the likedevices being operated with gas and/or steam. When providing such anejector, the driving medium 20 entering through a control valve 14 isaccelerated in a driving nozzle 12 and when entering into the suctionspace, vigorously entrains the medium to be delivered. The diffusor 13which follows the ejector nozzle 12 compresses the mixture of deliveringmedium and the driving jet (air or steam) up to the desired inductionpressure.

By connecting the suction space of the ejector with the first suctionduct 8 or the space 10 to be evacuated, an increase in inducted quantityQ, at the suction pressure p, can be attained. This will be elucidatedby a numerical example:

Assume that a pressure of 30 Torr obtains in the suction duct 8. Themixture of driving jet and delivering medium in the ejector 11 can thenbe condensed, for example, to 120 Torr. Since this pressure isconsiderably higher than that obtaining at the suction duct 8 of thepump, this mixture readily flows through the suction opening 6 into theinterior of the rotor cells located in the region of this additionalsuction opening 6 at a pressure of 30 Torr, whereafter it is condensedto 120 Torr. Thereafter the two gas quantities Q and Q which enter intothe vane cells through the suction ducts 8 and 7 are conjointly ejectedthrough the pressure opening 4 into the pressure duct 9 of the pump.

By means of the throttle valve 18 in the additional suction duct 7, thegas quantity additionally supplied to the pump through the suctionopening 6 can be controlled. This can be done, for example, in such amanner that the same gas quantity always passes through the pressureopening 4 independently of the pressure obtaining at the suction duct 8.

With any of the above-described arrangements according to the inventionthere results an overall improvement in efficiency of the pump. This isbecause the power demand of the pump is largely determined by thewater-ring friction, gap losses and other losses. Since these remain toa large extent constant with the invention, it remains only to raise thecompressing work for the additional gas entering through the suctionduct 7 or for the mixture of driving and delivering gas entering throughthe same duct.

By connecting to the additional suction opening a further apparatuswhich is to be evacuated at a somewhat higher suction pressure, forexample suction rollers for the paper industry, rotating filters or thelike equipment, then the usually required two different pumps aresubstituted by a sin gle pump operating with a considerably betteroverall efiiciency since the hydraulic losses (liquid-ring friction,slot and gap losses) are not appreciably increased additionally. Intotality, therefore, a reduced overall amount of machinery is afforded,also an improved efficiency as well as the avoidance of cavitation.

A further enlargement in the field of use of such a pump results if agas or steam ejector is connected ahead of the additional suctionopening. According to another feature of the invention it is also ofadvantage to connect the suction space of such an ejector and thefirst-mentioned suction opening with one and the same space or vessel tobe evacuated. This also results, in totality, in increasing the inductedquantity of gas and consequently the efficiency of the pump.

A pump according to the invention is advantageously applicable formixing and conveying gases and/or vapors for the purpose of performingchemical reactions within a space sealed with the aid of the liquid-ringpump. This is achieved as described above by supplying the two gaseousor vaporous reactants through the two suction openings respectively intothe pump.

Another significant advantage of the additional suction opening in apump according to the invention resides in the fact that this openingpermits inducting into the pump such a quantity of fluid andcompressible medium, for example gas, that even if the pressure ratiovaries greatly between the first suction opening and the pressureopening, the quantity of gas delivered through the pressure openingremains constant so that the pressure opening can be given a uniform andconstant outlet cross section. In this case valves of any kind are nolonger required. If desired in this case, the required quantity of airmay be supplied from an enclosed space, such as a vessel, that islikewise to be evacuated, and this supply can be controlled by amanually actuated or pressure-responsive throttle valve. It is furtherpossible to connect the additional suction opening through such athrottle valve directly with the ambient air or with the pressure spaceof the pump.

As already indicated, the invention is not limited to the illustratedand described embodiment but can be analogously applied to any otherdesign of gas pumps according to the liquid-ring type. This includesdesigns in which two or more working regions are provided along thehousing periphery of which each region comprises its own suction slotand pressure slot. Such twin pumps are known, for example, from theabove-mentioned US. Pat. No. 1,718,294 and US. Pat. No. l,797,980.

The invention is further applicable in the manner described above, topump designs in which the suction and pressure slots are not located inthe lateral control discs but are located in control cylinders orcontrol cones which laterally protrude into the rotor. The particularembodiment shown for illustration and description in the presentspecification comprises two rotor half-portions, each having one of thetwo control discs coordinated thereto. However, the two halfportions ofthe rotor can also be separated from each other by a partition locatedin the middle of the rotor and in the middle of the cylindrical housing,so that, by applying the invention, there will result a total of foursuction openings for four different suction pressures.

The invention also contemplates within its scope the provision of morethan one additional suction opening between the conventional suctionopening and pressure opening. ln'this case, each of the additionalopenings, seen in the rotational direction of the rotor, is tocommunicate with a cell space having a pressure higher than thatobtaining at the next-preceding additional suction opening.

As further shown on the drawing, another space or vessel 15 to beevacuated having a somewhat higher pressure than the space or vessel 10can be connected to the suction duct 7. This is preferably done so thatthe connection of vessel 15 can be effected in lieu of the ejector 11 orin addition thereto. For this purpose, the illustrated embodiment showsa shutoff valve 14 which in conjunction with the valve 18 affords thejustmentioned selective operation, although if desired another shutoffvalve may be provided in the branch conduit which extends from vessel 10to suction conduit 7 and contains the ejector l1.

In conclusion, it is of interest that cavitation in the abovedescribedpump according tothe invention can be avoided. This is achieved byinducting additional air into the pump so that the vapor contained inthe rotor cells is prevented from condensing.

Upon a study of this disclosure it will be apparent to those skilled inthe art that the invention permits of various modifications other thanthose particularly illustrated and described herein, without departingfrom the essential features of the invention and within the scope of theclaims annexed hereto.

We claim:

1. A gas pump of the liquid-ring type for pumping a medium, comprising arotor having impeller vanes uniformly distributed over its periphery, ahousing structure containing the rotor and forming around said rotor anannular racing space for a centrifugally formed ring of liquid havingrespective arcuately spaced localities where the liquid ring during pumpoperation enters the most and the least respectively into the intervanespaces of said rotor, said housing structure having a first suctionopening and a pressure opening at said localities and having respectivesuction and pressure duct means communicating with said space throughsaid two openings, said housing structure having at least one additionalsuction opening located between said first suction opening and saidpressure opening, said additional suction opening having its leadingend, relative to the direction of rotor rotation, spaced from thelagging end of said first suction opening an arcuate amount at leastequal to a vane division of said rotor, and another suction ductcommunicating with said space through said additional suction opening,said medium drawn through said first and additional suction openings andleaving said pump through said pressure opening.

2 In a gas pump according to claim 1, said additional suction openingextending to the region where said liquid ring reenters into saidintervane spaces of said rotor.

3. A gas pump according to claim 2, comprising control means connectedto said pump for supplying gas to said additional suction opening insufficient quantity to ensure that the quantity of gas at said pressureopening remains substantially constant and independent of changes ininduction pressure at said first suction opening.

4. A gas pump according to claim ll, comprising control means connectedinto said other suction duct for controlling the amount of fluid passingthrough said duct.

5 In a gas pump according to claim 4, said control means being athrottle valve which can be manually adjusted to control the flow of gasthrough said other suction duct.

6 In a gas pump according to claim 4, said control means being athrottle valve which operates in response to pressure to control theflow of gas through said other suction duct.

7. A gas pump according to claim 1, comprising a precompressor connectedto said other suction duct, said precompressor being operable with afluid for evacuating a chamber evacuated via said suction duct means.

8. In a gas pump according to claim 7, said precompressor being anejector, said ejector having a suction space connected with said suctionduct means.

1. A gas pump of the liquid-ring type for pumping a medium, comprising arotor having impeller vanes uniformly distributed over its periphery, ahousing structure containing the rotor and forming around said rotor anannular racing space for a centrifugally formed ring of liquid havingrespective arcuately spaced localities where the liquid ring during pumpoperation enters the most and the least respectively into the intervanespaces of said rotor, said housing structure having a first suctionopening and a pressure opening at said localities and having respectivesuction and pressure duct means communicating with said space throughsaid two openings, said housing structure having at least one additionalsuction opening located between said first suction opening and saidpressure opening, said additional suction opening having its leadingend, relative to the direction of rotor rotation, spaced from thelagging end of said first suction opening an arcuate amount at leastequal to a vane division of said rotor, and another suction ductcommunicating with said space through saiD additional suction opening,said medium drawn through said first and additional suction openings andleaving said pump through said pressure opening. CM,2Gas pump accordingto claim 1, said additional suction opening extending to the regionwhere said liquid ring reenters into said intervane spaces of saidrotor.
 3. A gas pump according to claim 2, comprising control meansconnected to said pump for supplying gas to said additional suctionopening in sufficient quantity to ensure that the quantity of gas atsaid pressure opening remains substantially constant and independent ofchanges in induction pressure at said first suction opening.
 4. A gaspump according to claim 1, comprising control means connected into saidother suction duct for controlling the amount of fluid passing throughsaid duct. 5 In a gas pump according to claim 4, said control meansbeing a throttle valve which can be manually adjusted to control theflow of gas through said other suction duct. 6 In a gas pump accordingto claim 4, said control means being a throttle valve which operates inresponse to pressure to control the flow of gas through said othersuction duct.
 7. A gas pump according to claim 1, comprising aprecompressor connected to said other suction duct, said precompressorbeing operable with a fluid for evacuating a chamber evacuated via saidsuction duct means.
 8. In a gas pump according to claim 7, saidprecompressor being an ejector, said ejector having a suction spaceconnected with said suction duct means.